1. Filed of the Invention
The invention, in general, relates to a novel method, compatible with modern ecological standards, of separating vaporous substances from gaseous media, such as, for example, air containing a high proportion of components having a low boiling point, and, more particularly, to a method of separating organic vapors from air exhausted or evacuated from refinery storage tanks and other liquid storage facilities and recovering them in liquified form.
2. Statement of the Prior Art
German patent application P 44 00 456.7-13discloses a method of simultaneously separating organic and inorganic vaporous substances from air or technical gases by direct condensation in a cold scrubber. As there disclosed, a circulating current of recovered condensates is utilized as the refrigerant in the cold scrubber. When operating in a range of moderate temperatures the refrigerant is supercooled by a cold-vapor refrigeration unit, and by a cold-air refrigeration unit when operating at demanding, i.e. very low ranges, temperature parameters. The low temperature component of the pure air is regeneratively utilized for cooling the refrigerant in an upper column of the cold scrubber or for precooling the compressed air of the cold-air refrigeration unit. However, such a process is not suitable for the separation from air of high proportions of light components, i.e components having a low boiling point, or of non-condensible organic substances, because at low overpressure levels and at ambient temperatures only a limited quantity of these components is solvable and can be withdrawn in liquid form at the bottom (sump) of the column. Consequently, the light components accumulate at the middle portion of the cold scrubber and, in the end, they remain within the air to be scrubbed.
Light hydrocarbons of the kind having one or two C atoms cannot be separated from air by condensation at temperatures above -150.degree. C. (.apprxeq.-101.degree. F.); they are, under such conditions, considered to be non-condensible. In thermal separation processes of substances products not derived from the process itself should preferably not be used as auxiliary agents, lest additional contaminations and additional separation problems result which, in turn, further complicate the production of pure process-integrated substances.